Hi everyone,

I have a 2018 Audi A4 B9 and recently installed an aftermarket OEM-style ambient lighting kit (ATW controller with MMI integration).

The installation is now fully working:

• Ambient lighting works in all areas.
  
• The OEM Ambient Lighting menu is visible in the MMI.
  
• Colors and brightness can be controlled through the MMI.
  
• The app connects and controls the lights correctly.
  
• All windows work.
  
• Mirrors work.
  
• Central locking works.
  
• No warning messages appear on the dashboard while driving.
  

During the installation I initially had some issues:

• "Shift P before leaving vehicle" warning because one connector was not connected correctly.
  
• Front window switches were not working because the door connectors were not fully seated.
  

After correcting those installation mistakes, all functions returned to normal and there are currently no visible problems with the car.

However, after clearing all faults and driving for about 15 minutes, I consistently get the following two DTCs back:

U150600 - Local Data Bus 5
No Communication

U150700 - Local Data Bus 6
No Communication

Both faults are stored in module 09 (Central Electrics).

Additional information:

• Faults can be cleared successfully.
  
• After driving they return.
  
• No dashboard warnings appear.
  
• No electrical functions seem to be affected.
  
• Ambient lighting continues to work perfectly.
  
• Windows, mirrors and door functions all operate normally.
  
• The vehicle starts and drives normally.
  

My question is:

Has anyone seen U150600 and U150700 after installing aftermarket ambient lighting on a B9 platform?

Could these faults be caused by the ambient lighting controller communicating on the LIN bus, or do they indicate that a specific module is still not connected correctly even though all functions appear to work?

Any advice or experience with these two fault codes would be appreciated.

Thanks!

 

So I just installed similar lights, and my biggest issue was missed plugs or wires not installed correctly. All were from crappy instructions or poor videos that I followed. Once all that was fixed, all my errors went away.

I suggest you pull it all apart and double check your plugs. Something may have been missed.

 

I did a quick search, and there was a TSB for the Q7 about some wires in the driver's side foot well fuse box that would get corroded and cause the same error messages.

You may want to check the same fuse box, especially if that is the one you tapped into.

 

Update:

I did some additional testing.

I moved the ACC wire of the ambient lighting controller to the same ACC source used by my aftermarket pop-up tweeters. After that, I cleared all fault codes and drove the car for about 20 minutes.

After the drive, I performed another full scan and the faults were gone. At that point, U150600 and U150700 did not return.

However, after the car sat for approximately one day, I scanned it again and both faults had returned:

• U150600 - Local Data Bus 5: No Communication
  
• U150700 - Local Data Bus 6: No Communication
  

Everything in the car continues to work correctly:

• Ambient lighting works perfectly
  
• OEM MMI ambient lighting menu works
  
• Pop-up tweeters work correctly
  
• Windows, mirrors and locks all work
  
• No warning messages on the dashboard
  

I also checked whether the ambient lighting controller goes to sleep. After locking the vehicle and waiting 30-40 minutes, the ATW Bluetooth device is no longer visible, which suggests the controller is entering sleep mode correctly.

One thing I have noticed is that after the car sits for around two days, battery voltage is approximately 12.0V (sometimes slightly below) and the engine cranks a little longer than before. The battery may still be the original 2018 battery.

At this point I am wondering whether the battery condition could be contributing to these communication faults, or whether they are simply caused by the aftermarket ambient lighting/tweeter retrofit.

Have you or anyone experienced something similar on a B9 platform?

 

I would still look at the driver foot well fuse box, since we know those codes link there on the TSB. That is all you really have to go on right now.

 

J519 T73A (large, middle)
pin 22 - LIN bus ? // direct -> wiper motor system J400
pin 23 - LIN bus ? // direct -> rain light sensor G397
pin 24 - LIN bus 2 // B549 -> overhead unit WX3; homelink transceiver J530; homelink controls E284; auto dimming mirror Y7
pin 25 - LIN bus 7 // B712 -> front left seat V512 & V514 ventilation motors; front right seat V516 & V518 ventilation motors
pin 26 - n/c
pin 27 - LIN bus 6 // B711 -> W74 / L194 front console ambient light 2; front left door; front right door; rear left door; rear right door
pin 28 - LIN bus 5 // B710 -> W45 rear left footwell lamp (in front left seat); W46 rear right footwell lamp (in front right seat) [RGB rear footwell lamps were deleted for the facelift]

J519 T54C (small, side)
pin 50 - LIN bus ? // direct -> light switch E1
pin 51 - LIN bus ? // direct -> driving/convenience controls unit E791 (the row of buttons above the cupholders)
pin 52 - n/c
pin 53 - LIN bus ? // A262 - > daisy chain 1 [K268 front left foot well lamp -> K269 front right foot well lamp]; daisy chain 2 [L243 -> L244 -> L245 instr panel contour lamps 1/2/3]

The daisy chain RGB elements on A262 are actually powered directly by the J519:
pin 1 - green, power from J519 T73A pin 59
pin 2 - LIN bus in
pin 3 - LIN bus out
pin 4 - brown, to chassis ground

The RGB elements on B710 (W45, W46) are also powered directly by the J519:
pin 1 - green, power from J519 T73A pin 11
pin 2 - LIN bus in
pin 3 - n/c
pin 4 - brown, to chassis ground
As noted above, Audi cost cut RGB for the rear footwell lamps at the facelift. So there's no LIN wire to the seat mounted rear footwell lamps in facelifts.

So what about the RGB elements on B711? It appears the door elements are also powered by the T73A pin 59. The front console ambient light seems to depend on if it's white (in which case, it's by pin 11) or RGB (then it's pin 59).


The codes have nothing to do with the fuse box directly. The codes say only exactly "I'm trying to run a LIN bus on pin X, and I'm not getting any response that I should be getting". Why that is requires actual troubleshooting.

Is there a poor connection that is flaking out on either the LIN or power wiring? Is it this third party device (is the device actually attached to the two LIN buses and acting on behalf of the RGB elements) not well. Is this third party device not emulating all the devices the J519 is expecting present on the bus? Because it's no comms, but no comms with who. With no one, or with an expected slave device? Or is it a when issue; is the aftermarket too slow to boot so it's not responsive to the J519 queries until after the J519's patience has run out?


In the end, if everything is functionally working as you want, leave it be. Those two codes are about two LIN buses that have no bearing on the operation of any important vehicle components. If it's just a interop conflict between the J519 and the aftermarket, but everything that needs to be happening is happening, there's no value in working out the interop issue. Not at this time.

But I wouldn't push the battery voltage thing under the mat. That needs to be looked into. Maybe it is an aging battery, maybe it's either aftermarket device not entirely sleeping. If it's normal for the car to sit around for more than a day unused, pull the power to the aftermarkets and lock it up and see if it again is low when you return after a long sleep. Also, you should be able to pull that kind of data from the log values in the gateway.